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      Func vs. Action vs. Predicate

      时间:2023-11-11
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                本文介绍了Func vs. Action vs. Predicate的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着跟版网的小编来一起学习吧!

                问题描述

                有真实的例子和他们的使用,有人可以帮助我理解:

                With real examples and their use, can someone please help me understand:

                1. 我们什么时候需要 Func 委托?
                2. 我们什么时候需要 Action<T>委托?
                3. 我们什么时候需要 谓词<T>委托?

                推荐答案

                FuncAction 的区别只是你是否希望委托返回一个值(使用Func) 与否(使用 Action).

                The difference between Func and Action is simply whether you want the delegate to return a value (use Func) or not (use Action).

                Func 可能是 LINQ 中最常用的——例如在投影中:

                Func is probably most commonly used in LINQ - for example in projections:

                 list.Select(x => x.SomeProperty)
                

                或过滤:

                 list.Where(x => x.SomeValue == someOtherValue)
                

                或按键选择:

                 list.Join(otherList, x => x.FirstKey, y => y.SecondKey, ...)
                

                Action 更常用于 List<T>.ForEach 之类的事情:对列表中的每个项目执行给定的操作.我使用它的频率低于 Func,尽管我 确实 有时将无参数版本用于 Control.BeginInvokeDispatcher.BeginInvoke.

                Action is more commonly used for things like List<T>.ForEach: execute the given action for each item in the list. I use this less often than Func, although I do sometimes use the parameterless version for things like Control.BeginInvoke and Dispatcher.BeginInvoke.

                Predicate 实际上只是一个特殊的 Func,在所有 Func 和大部分 之前引入>Action 代表出现了.我怀疑如果我们已经有各种形式的 FuncAction ,那么 Predicate 就不会被引入......尽管它确实赋予委托的使用某种意义,而 FuncAction 用于广泛不同的目的.

                Predicate is just a special cased Func<T, bool> really, introduced before all of the Func and most of the Action delegates came along. I suspect that if we'd already had Func and Action in their various guises, Predicate wouldn't have been introduced... although it does impart a certain meaning to the use of the delegate, whereas Func and Action are used for widely disparate purposes.

                Predicate 主要用于 List<T> 中,用于 FindAllRemoveAll 等方法.

                Predicate is mostly used in List<T> for methods like FindAll and RemoveAll.

                这篇关于Func vs. Action vs. Predicate的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持跟版网!

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